I stopped by Autozone this evening and the closest thing I found to copper tubing was this kit by Sunpro (CP7584). I went ahead and bought it in case this is what I need, in which case and have it on hand and ready to go.

It turns out there is a listing for more copper tubing on the website (Gauge Line Tubing), but I didn't see any of it at the store I went to.

Hoping to do a check on the original tubing before heading to work tomorrow.